American drugmaker Pfizer, who partnered with Germany's BioNTech to develop the COVID-19 vaccine, has predicted a much higher revenue for the 2021 year on Wednesday, forecasting the delivery of 500 million more vaccine doses compared to earlier expectations.

It estimates delivering 2.1 billion doses and generating $33.5 billion in sales. The company's May forecast was for $26 billion in sales.

Pfizer also lifted its full-year profit outlook as well as the expected range for 2021 revenues.

Pfizer Chief Executive Albert Bourla said more than a billion doses of the vaccine have been delivered, saying "the speed and efficiency of our efforts with BioNTech to help vaccinate the world against COVID-19 have been unprecedented."

Pfizer said the pre-tax profit margin on the COVID-19 vaccine sales was in the "high-20s" in terms of percent, the same as the earlier forecast.

Pfizer reported second-quarter profits of $5.6 billion, up 59% from the year-ago period on 92% increase in revenues to $19 billion.

Pfizer has launched clinical studies on a possible third dose of the COVID-19 vaccine as a booster shot. Bourla has said such boosters could amount to a "durable" revenue stream for the company.

Thus far, American health officials have far backed a third shot for the broad population, but officials are studying the need for a third shot in immuno-compromised people.

Shares of Pfizer declined 0.5% to $41.88 in pre-market trading.